Yanase, Keiichi and Obikane, Miku and Ogura, Taku and Buchner, Richard and Igarashi, Akinori and Sato, Takaaki (2018) Ion fluctuations and intermembrane interactions in the aqueous dispersions of a dialkylchain cationic surfactant studied using dielectric relaxation spectroscopy and small- and wide-angle X-ray scattering. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20 (41). pp. 26621-26633. ISSN 1463-9076, 1463-9084
Full text not available from this repository. (Request a copy)Abstract
A dialkylchain cationic surfactant forms the so-called -gel in water showing virtually no fluidity, which is transformed into a highly fluidic dispersion upon addition of a small amount of salt. This intriguing phenomenon is utilized in household industries. However, the underlying mechanisms remain unclear. Here, we use dielectric relaxation spectroscopy (DRS) and simultaneous small- and wide-angle X-ray scattering (SWAXS) to shed light on this issue. We find that an excess amount of CaCl2 induces an -gel-to-multi-lamellar vesicle (MLV) transition accompanied by a marked increase of the reservoir volume fraction. This resembles an unbound lamellar-to-bound lamellar transition that cannot be explained without invoking a weak long-ranged electrostatic attraction. The DRS data provide evidence that the counterions fluctuate both vertically and laterally at the interface, whose relaxation amplitudes sharply depend on a percolating state of an aqueous phase. The strikingly small bulk-water amplitude is likely to reflect depolarizing electric fields induced by the MLV architecture, along with genuine hydration effects. The modified Caille approach to the SAXS intensities reveals sensitive salt-concentration dependent membrane-membrane interactions. The least undulating membranes are formed at a salt concentration of ca. 10 mmol L-1. Above 25 mmol L-1, where small surface separation (<2.5 nm) is attained, far more undulating membranes than those predicted by the Helfrich interaction are produced. This suggests that the hydration forces, generally believed to induce strong short-range repulsion, do not suppress the membrane undulation fluctuations.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CHARGED SPHERICAL-PARTICLES; SPONTANEOUS VESICLES; ELECTROSTATIC INTERACTION; SOLVENT RELAXATION; LAMELLAR PHASES; COUNTERION; HYDRATION; FORCES; MEMBRANES; MIXTURES; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > PD Dr. Richard Buchner |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 10 Oct 2019 06:47 |
| Last Modified: | 10 Oct 2019 06:47 |
| URI: | https://pred.uni-regensburg.de/id/eprint/13553 |
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